Re: [avr-gcc-list] more detailed UART Problems

[Jason Kyle]

At 04:17 5/04/2002, Karsten Becker wrote:
> Hi everybody,
> I found this very interesting piece of code that makes problems.
> #include <progmem.h>
> #include "uart.h"
> u08 newval=0xFF,oldval=0xFF;
> int main(void) {
>    UART_Init();
>    outp(0x00,DDRA);
>    for (;;) {
>        newval=inp(PINA);
>        if (newval!=oldval) {
>            oldval=newval;
>            PRINT("Dumping memory");
>            EOL();
>        }
>    }
> }
>
> SIGNAL(SIG_UART_RECV) {
>    UART_RxChar = inp(UDR);
> }

Try reading USR first, check FE bit in case there was a framing error.  If 
you don't read USR there are some strange symtoms as you note.

Jason Kyle

PS No warranty on the code below!

if (inp(USR) & BV(FE)) {
        inp(UDR);
        /* Code to handle framing error */
}
else {
        UART_RxChar = inp(UDR);
        /* Do whatever */

}




> The symtom is, when you reset the 8535 and press a switch, the Text 
> Dumping memory is send normally. But when you send a char to the µC and 
> then press the switch just the big D is written to the terminal.
> Maybe someone has an idea.
> Thanks,
> Karsten

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